JP4440068B2 - Blue phosphor - Google Patents

Description

  The present invention relates to a phosphor that emits blue light when excited by vacuum ultraviolet light, which is useful as a blue light emitting material for a plasma display panel (hereinafter referred to as PDP) or a rare gas lamp.

As a blue phosphor that emits blue light when excited by ultraviolet rays or vacuum ultraviolet rays, CaMgSi ₂ O ₆ : Eu ²⁺ (hereinafter referred to as CMS) in which a part of calcium of diopside (CaMgSi ₂ O ₆ ) is replaced with europium. : Eu ²⁺ ) is known. CMS: Eu ²⁺ emits light with a stable crystal structure compared to BaMgAl ₁₀ O ₁₇ : Eu ²⁺ (hereinafter referred to as BAM: Eu ²⁺ ), which is widely used as a blue light emitting material for PDP and rare gas lamps. There is a feature that efficiency is less likely to decrease over time. However, it is already known that the emission intensity of CMS: Eu ²⁺ blue phosphor is lower than that of BAM: Eu ²⁺ blue phosphor. Therefore, development of a CMS: Eu ²⁺ blue phosphor with high emission intensity is desired.

The CMS: Eu ²⁺ blue phosphor can be synthesized by mixing a calcium compound, a europium compound, a magnesium compound, and a silicon compound and firing at a temperature of 1000 ° C. or higher.
Non-Patent Document 1 discloses CMS: Eu ²⁺ containing silicon dioxide produced by mixing and firing calcium carbonate, magnesium carbonate, silicon dioxide, and europium fluoride so that the amount of silicon dioxide exceeds the theoretical ratio. A blue phosphor is described. According to the description of Non-Patent Document 1, the emission intensity of the CMS: Eu ²⁺ blue phosphor increases as the charged amount of silicon dioxide increases, and is about the maximum with respect to the emission intensity of BAM: Eu ^2+. 74%.

Non-Patent Document 2 reports X-ray diffraction patterns of CMS: Eu ²⁺ blue phosphors having different europium contents. In the X-ray diffraction pattern described in Non-Patent Document 2, CMS: Eu ²⁺ blue phosphor has Ca ₂ MgSi ₂ O ₇ (Okermanite) and Ca ₂ Eu ₈ (SiO ₄ ) ₆ O ₂ as impurities. In particular, it is shown that ochermanite is likely to be mixed when the europium content is 0.02 mol or more.
Ryo Yoshimatsu, Satoshi Honda, Takashi Kunimoto, Tadashi Tokusaku, Sho Tanaka, Hiroshi Kobayashi, "Vacuum UV Excited Phosphor CaMgSi2O6: Eu2 + Emission Characteristics", IEICE Technical Report, The Institute of Electronics, Information and Communication Engineers, 2001 July, p. 37-42 Takashi Kunimoto, “Characteristics of PDP (Plasma Display) and the latest developments” PDP book issuance seminar, published by Information Organization, July 23, 2004, p. 9

An object of the present invention is to exhibit an emission intensity equivalent to or close to the emission intensity of a CMS: Eu ²⁺ blue phosphor having a high emission intensity, particularly BAM: Eu ²⁺ blue phosphor (particularly, BAM: Eu ²⁺ blue fluorescence). The object of the present invention is to provide a CMS: Eu ²⁺ blue phosphor exhibiting an emission intensity of 80% or more of the emission intensity of the body.

The present inventor has examined in detail the relationship between the impurities of the CMS: Eu ²⁺ blue phosphor and the emission intensity. As a result, it was found that the emission intensity of the CMS: Eu ²⁺ blue phosphor tends to decrease as the mixed amount of akermanite increases.

The present invention has the same crystal structure as diopside, the basic compositional formula _{Ca p Eu q Mg x Si y} O z (p, 0.90~0.985, q is from 0.1 to 0. 015, x is 0.95 to 1.05, y is 1.90 to 2.10, z is p + q + x + 2y, and q / (p + q) is 0.015 to 0.10) The phosphor is a blue phosphor in which an akermanite X-ray diffraction pattern is not detected from an X-ray diffraction pattern measured under the following measurement conditions .
[ X-ray diffraction pattern measurement conditions]
Measurement: Continuous measurement
X-ray source: CuKα
Tube voltage: 50 kV
Tube current: 150 mA
Divergent slit width: 1/2 deg
Scattering slit width: 1/2 deg
Light receiving slit width: 0.15 mm
Scan speed: 5 deg / min
Scan step: 0.02 deg

The X-ray diffraction peak corresponding to the (−221) plane of the diopside corresponds to an X-ray diffraction peak having an angle of 2θ of 29.7 degrees in the X-ray diffraction pattern measured under the following conditions. The X-ray diffraction peak corresponding to the (211) plane of one akermanite corresponds to an X-ray diffraction peak having an angle of 2θ of 31.1 degrees in the X-ray diffraction pattern measured under the following conditions.
[Measurement conditions of X-ray diffraction pattern]
Measurement: Continuous measurement X-ray source: CuKα
Tube voltage: 50 kV
Tube current: 150 mA
Divergent slit width: 1/2 deg
Scattering slit width: 1/2 deg
Light receiving slit width: 0.15 mm
Scan speed: 5 deg / min Scan step: 0.02 deg

The present invention also provides calcium carbonate powder, europium compound powder, magnesium oxide powder, and silicon dioxide powder with a Ca: Eu: Mg: Si molar ratio of 0.90 to 0.985: 0.1 to 0.015: 0. .95 to 1.05: 1.90 to 2.10 (provided that Eu / (Ca + Eu) = 0.015 to 0.10) is fired at a temperature of 1000 to 1500 ° C. It has the same crystal structure as diopside, and the basic composition formula is Ca _p Eu _q Mg _x Si _y O _z (P is 0.90 to 0.985, q is 0.1 to 0.015, x is 0.95 to 1.05, y is 1.90 to 2.10, and z is p + q + x + 2y. , And q / (p + q) is 0.015-0.10), and the height of the X-ray diffraction peak corresponding to the (211) plane of the akermanite is diopside (- 211) a blue phosphor that is 1/50 or less the height of the X-ray diffraction peak corresponding to the plane.

The CMS: Eu ²⁺ blue phosphor of the present invention exhibits an emission intensity equivalent to or close to that of the BAM: Eu ²⁺ blue phosphor. Therefore, it can be advantageously used as a blue fluorescent material for PDP and rare gas lamps. In addition, by using the method for producing a blue phosphor of the present invention, it is possible to produce a CMS: Eu ²⁺ blue phosphor that is not mixed with or has a very small amount of mixed akermanite. Become.

The CMS: Eu ²⁺ blue phosphor of the present invention has a molar ratio of 0.90 to 0.985: 0.1 to 0.015: 0.95 to 1.05: 1 for calcium, europium, magnesium and silicon, respectively. .90 to 2.10, and the content of europium is in the range of 1.5 to 10 mol% with respect to the total content of calcium and europium, preferably 0.018 to 0.8. It is in the range of 050. The CMS: Eu ²⁺ blue phosphor of the present invention can be represented by the following general formula (I).

_{(I) Ca p Eu q Mg} x Si y O z

In the formula (I), p is 0.90 to 0.985, q is 0.1 to 0.015, x is 0.95 to 1.05, y is 1.90 to 2.10, z is p + q + x + 2y and q / (p + q) is 0.015 to 0.10 (preferably 0.018 to 0.050).

In the CMS: Eu ²⁺ blue phosphor obtained by the production method of the present invention, the height of the X-ray diffraction peak corresponding to the (211) plane of akermanite is X-ray diffraction corresponding to the (−221) plane of the diopside. The main characteristic is that the peak height is 1/50 or less, preferably 1/100 or less, and no akermanite is mixed, or the amount of the akermanite is extremely small.

The CMS: Eu ²⁺ blue phosphor of the present invention can be preferably manufactured by firing a mixed powder composed of calcium carbonate powder, europium compound powder, magnesium oxide powder and silicon dioxide powder at a temperature of 1000 to 1500 ° C. it can. This blue phosphor manufacturing method is mainly characterized by using magnesium oxide powder as a magnesium source.

The calcium carbonate powder used for the production of the CMS: Eu ²⁺ blue phosphor of the present invention preferably has a purity of 99% by mass or more, particularly preferably 99.9% by mass or more. The calcium carbonate powder preferably has an average particle size in the range of 0.1 to 5.0 μm.

  The magnesium oxide powder preferably has a purity of 99% by mass or more, particularly preferably 99.9% by mass or more. The magnesium oxide powder preferably has an average particle size in the range of 0.1 to 3.0 μm. As the magnesium oxide powder, a powder obtained by a method of contacting metal magnesium vapor with oxygen (gas phase oxidation reaction method) can be preferably used.

  As the europium compound powder, a europium fluoride powder, a europium oxide powder, or a europium chloride powder can be used. Europium fluoride powder and europium oxide powder are preferred, and europium fluoride powder is particularly preferred. The europium compound powder preferably has a purity of 99% by mass or more, particularly preferably 99.5% by mass or more. The europium compound powder preferably has an average particle size in the range of 0.1 to 5.0 μm.

  The silicon dioxide powder preferably has a purity of 99% by mass or more, and particularly preferably 99.5% by mass or more. The silicon dioxide powder preferably has an average particle size in the range of 1 to 50 μm.

In the production of the CMS: Eu ²⁺ blue phosphor of the present invention, the above-mentioned calcium carbonate powder, europium compound powder, magnesium oxide powder, and silicon dioxide powder were mixed at a molar ratio of Ca: Eu: Mg: Si of 0.90. ˜0.985: 0.1 to 0.015: 0.95 to 1.05: 1.90 to 2.10 (where Eu / (Ca + Eu) = 0.015 to 0.10) In addition, a mixed powder is prepared using a mixer such as a ball mill. The mixing of the powder is preferably performed in an organic solvent such as methanol, ethanol, acetone or the like.

  The mixed powder obtained in the above step is fired at a temperature of 1000 to 1500 ° C. Firing of the mixed powder is preferably performed in a reducing atmosphere. Specifically, the mixed powder is preferably fired in argon gas or nitrogen gas containing hydrogen gas in a range of 1 to 10% by volume. The firing time is generally in the range of 1 to 100 hours.

It is known that the CMS: Eu ²⁺ blue phosphor of the present invention obtained as described above is less susceptible to deterioration over time than BAM: Eu ²⁺ . Further, the CMS: Eu ²⁺ blue phosphor of the present invention exhibits an emission intensity that is equal to or close to that of the BAM: Eu ²⁺ blue phosphor. Therefore, the CMS: Eu ²⁺ blue phosphor of the present invention can be advantageously used over a long period of time as a blue fluorescent material for PDP and rare gas lamps.

[Example 1]
Calcium carbonate (purity: 99.99% by mass, average particle size: 3.87 μm), europium fluoride (purity: 99.9% by mass, average particle size: 2.71 μm), magnesium oxide (by vapor phase oxidation method) What was produced, purity: 99.99% by mass, average particle size: 0.66 μm), and silicon dioxide (purity: 99.9% by mass, average particle size: 49.8 μm) of Ca: Eu: Mg: Si Each was weighed so that the molar ratio was 0.98: 0.02: 1.00: 2.00, and wet-mixed in an ethanol solvent using a ball mill for 24 hours. The obtained mixed powder was dried to evaporate ethanol. The mixed powder after drying was put in an alumina crucible and fired at a temperature of 1150 ° C. for 6 hours in a 2% by volume hydrogen-98% by volume argon atmosphere.

When the X-ray diffraction pattern of the fired product produced as described above was measured under the above conditions, the diopside X-ray diffraction pattern was confirmed from the obtained X-ray diffraction pattern, and Ca _0.98 Eu _0.02 MgSi ₂ It was confirmed that O ₆ was formed. On the other hand, no X-ray diffraction pattern of akermanite was confirmed from the X-ray diffraction pattern of the fired product.

  The emission spectrum of the fired product was measured with a spectrofluorometer having an excitation wavelength of 254 nm. The result is shown in FIG.

[Comparative Example 1]
Except for changing the magnesium oxide in Example 1 to basic magnesium carbonate (purity: 42.0% by mass as magnesium oxide, average particle size: 15.3 μm), the same operation as in Example 1 was performed to obtain the fired product. Manufactured.

When the X-ray diffraction pattern of the fired product was measured under the above conditions, the X-ray diffraction pattern of diopside and akermanite was confirmed from the obtained X-ray diffraction pattern, respectively, and Ca _0.98 Eu _0.02 MgSi _2. It was confirmed that O ₆ and kermanite were formed. The height of the X-ray diffraction peak corresponding to the (211) plane of the akermanite was 15/100 of the height of the X-ray diffraction peak corresponding to the (-221) plane of the diopside.
The emission spectrum of the fired product was measured under the same conditions as in Example 1. The result is shown in FIG.

[Reference Example 1]
The emission spectrum of commercially available BAM: Eu ²⁺ was measured under the same conditions as in Example 1. The result is shown in FIG.

In FIG. 1, the horizontal axis indicates the wavelength of emitted light, the vertical axis indicates the emission intensity, and the relative emission intensity when the maximum emission intensity of BAM: Eu ²⁺ is 1.0. From the results shown in FIG. 1, it can be seen that the emission intensity decreases as the amount of kermanite mixed increases. In particular, Ca _0.98 Eu _0.02 MgSi ₂ O ₆ (Example 1), in which the X-ray diffraction pattern of akermanite was not detected, has a relative emission intensity of about 85% with respect to BAM: Eu ²⁺ , and the conventionally known CMS : It turns out that it shows high luminescence intensity compared with Eu < ²⁺ >.

It is an emission spectrum of the baked product (Ca _0.98 Eu _0.02 MgSi ₂ O ₆ ) and BAM: Eu ²⁺ produced in Example 1 and Comparative Example 1.

Claims (3)

Have the same crystal structure as diopside, the basic compositional formula _{Ca p Eu q Mg x Si y} O z (p, 0.90~0.985, q is, from .1 to .015, x is 0.95 to 1.05, y is 1.90 to 2.10, z is p + q + x + 2y, and q / (p + q) is 0.015 to 0.10). In addition, a blue phosphor in which an akermanite X-ray diffraction pattern is not detected from an X-ray diffraction pattern measured under the following measurement conditions :
[ X-ray diffraction pattern measurement conditions]
Measurement: Continuous measurement
X-ray source: CuKα
Tube voltage: 50 kV
Tube current: 150 mA
Divergent slit width: 1/2 deg
Scattering slit width: 1/2 deg
Light receiving slit width: 0.15 mm
Scan speed: 5 deg / min
Scan step: 0.02 deg. A calcium carbonate powder, a europium compound powder, a magnesium oxide powder and a silicon dioxide powder are mixed at a Ca: Eu: Mg: Si molar ratio of 0.90 to 0.985: 0.1 to 0.015: 0.95 to 1.50. 05: 1.90 to 2.10 (however, Eu / (Ca + Eu) = 0.015~0.10) consists of calcining a mixed powder containing at become amounts at a temperature of 1000 to 1500 ° C., have the same crystal structure as diopside, the basic compositional formula _{Ca p Eu q Mg x Si y} O z (p, 0.90~0.985, q is, from .1 to .015, x is 0.95 to 1.05, y is 1.90 to 2.10, z is p + q + x + 2y, and q / (p + q) is 0.015 to 0.10). The height of the X-ray diffraction peak corresponding to the (211) plane of ochermanite The manufacturing method of the blue fluorescent substance whose length is 1/50 or less of the height of the X-ray-diffraction peak corresponding to the (-211) plane of a diopside .   The method for producing a blue phosphor according to claim 2, wherein the average particle diameter of the magnesium oxide powder is in the range of 0.1 to 3.0 µm.

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